Safety device for boilers



May 9, 1939. F. L. CORMJER ET AL SAFETY DEVICE FOR BOILERS Filed Aug. 18, 1956 fTLCoI-mzz' H L. L ariao rz.

a a/m 62f ozheya Patented May 9, 1939 UNITED STATES PATENT OFFICE SAFETY DEVICE FOR BOILERS Frank L. Cormier, East Braintree, and Harold L. Larson, East Weymouth, Mass.

This invention relates to safety devices for boilers whereby damage to the boiler is prevented should the water therein fall to a dangerous level. We are aware that devices for this purpose have heretofore been known and used which automatically sound an alarm or shut oh the fuel or burner when a dangerous water level is reached, but such devices have been quite complex and of a nature rendering them objectionable for various reasons, among which rea-= sons may be particularly mentioned the difficulty of resetting the device or replacing parts there of. The primary object of our invention is to produce an improved, relatively simple and inexpensive safety device for this purpose which may be easily installed and conveniently reset or renewed.

Our invention relates more particularly to an oil burning boiler wherein the burner is controlled by a switch. This switch, or other burner controlling means, is positioned to be operated by outward movement of a spring-loaded rod extending through a packing in the outer wall of the boiler and having its inner end anchored by soft metal within a plug threaded into the crown sheet of the boiler. The plug is removable and replaceable from the furnace side of the crown sheet whereby the device can be repaired or the plug renewed easily at little expense. Should the water fall below the plug the soft metal melts and releases the rod which thereupon moves outwardly and operates the burner switch. The production of such an improved device, particularly adapted for use with oil burning boilers, comprises a further object of our invention.

These and other features of the invention will be best understood and appreciated from the following description of a preferred embodiment thereof, selected for purposes of illustration and shown in the accompanying drawing, wherein Fig. 1 is an elevation of a preferred embodiment of our invention, partially broken away and 45 in section.

Fig. 2 is a front view, partially in section, of a portion of the device.

Fig. 3 is an enlarged sectional view of our improved anchoring plug.

Fig. 4 is a detail view of the anchor member.

In the drawing, l0 indicates the outer wall of the boiler and I2 the crown sheet thereof. The boiler is illustrated as oil fired by a motor driven burner l4 controlled by a switch IS, the switch being closed when the switch arm I6 is in the down position and being open when the arm is in the up position.

Cooperating with the switch arm is a rod l8 extending through the wall i0 and having its inner end anchored by soft metal within a plug 20 threaded into the crown sheet. A packing 2| is provided for the rod at the wall Hi, this packing being held between an outer plug 22 threaded into the wall and an inner plug 24 threaded into the plug 22. The rod is normally moved outwardly by a spring 25 carried on the rod between. the plug 24 and a collar 26. The collar is preferably permanently secured to the rod as by a non-removable pin 21 whereby the position of the collar cannot be readily changed. The switch may be conveniently supported on a bracket 28 held firmly on the plug 22 by a lock-nut 30 and a second bracket 32 serves as a guide for the rod. The switch arm I6 is positioned in alignment with the rod andthe length of. the rod is-such that outward movement thereof by means of the spring opens the switch.

Our improved anchoring plug 20 has an open bore in its forward end and is of restricted diameter at 34 intermediate the ends of the bore. While the plug may be made in one piece we prefer to construct it of two pieces wherein a plug- 35 threaded into the rear end of the main body member provides a closure for the .rear end of the bore. Seated within the forward end of the bore is an anchor 36 of somewhat conical shape and having an anchoring shoulder 31 on its outer surface. The anchor-is held within the bore by soft metal 38 and in .a position wherein said shoulder is adjacent to the restricted diameter 34. Such an arrangement provides a substantial body of soft metal but leaves a relatively thinner body thereof at 34 which melts more readily and thereupon releases the rod.

' The anchor is provided with a threaded hole 48 for receiving the threaded end of the rod 18.

The simplicity and utility of our invention is believed to be obvious. The installation requires only two tapped holes in the walls I0 and [2 for receiving the plugs 22 and 20. The plug 20 is threaded tightly into its hole, as indicated in Fig. 1, and the plug 22 is threaded tightly into its hole in like manner, the rod l8 being connected to the anchor 36 merely by rotating the rod to thread it into the hole 40. When the spring-loaded rod is thus threaded into the anchor the rod is held down to the position of Fig. 1 wherein its top end is below the lowermost position of. the switch arm l6. As long as the plug 20 is covered with water the soft metal 38 holds the anchor and rod in the position indicated. Should the water fall below the position indicated at 34, the soft metal will melt sufiiciently to release the rod which thereupon is moved upwardly by the spring and throws the switch to the open position indicated in broken lines, it being understood that such action stops the burner l4 and thereby eliminates damage to the boiler. It should be particularly noted that the plug 29 extends upwardly into the boiler to such an extent that scale forming on the wall I2 does not interfere with the. action of the device. It will furthermore be apparent that the bore within the plug 20 is so formed that the anchor 36 is secured by a relatively thin ring of soft metal at 34, thus making the device very sensitive.

An important feature of our invention is the novel construction providing for easy replacement of the plug 20 by a new plug, either when the rod has been released by melting of the soft metal 38 or when it is thought advisable to provide a new plug. Such replacement requires only that the old plug 20 shall be removed and a new plug threaded in lieu thereof into the wall I2, the rod l8 being threaded into the anchor 36 as above stated. The rod is preferably of bronze or brass or such material as will not corrode under the action of water. It will now be apparent that we have produced a relatively simple and inexpensive device for boilers which can be readily installed and renewed as occasion requires.

It is well known that scale forming on the highly heated portion of the crown sheet insulates the cooling efiect of the water therefrom and, when scale thus forms on a specific area of the crown sheet, such area occasionally becomes so hot that the boiler pressure forces the same inwardly of the firebox to a bulging position. The plug 20 of our device is threaded into the hottest portion of the crown sheet and it is pointed out that the device is particularly adapted to care for the scale possibility above referred to. Scale forming on and over the plug 20 insulates the ring of soft metal at 34 from the cooling effect of the water sufficiently to permit the metal to soften and the anchor 36 to draw therefrom should the crown sheet bulge inwardly of the firebox, it being apparent that the ring of soft metal renders the device sufficiently sensitive to perform this function.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is,--

1. A threaded plug having an open bore in its forward end, an anchoring element in the bore,

and soft metal holding the anchoring element in the bore, the anchoring element having a thread ed hole in its forward end for receiving the threaded end of a rod, the plug being adapted to be threaded inwardly into a threaded hole through a boiler Wall with said forward end thereof projecting into the boiler chamber.

2. A threaded plug having a bore therethrough of restricted diameter intermediate the ends of the bore, an anchoring element in the forward end of the bore having a forwardly facing shoulder located adjacent to said restricted diameter, soft metal in the bore in holding contact with said shoulder whereby preventing forward movement of the anchoring element, and a plug threaded into the rear end of the first named plug and providing a closure for the rear end of the bore, the first-named plug being adapted to be threaded inwardly into a threaded hole through a boiler wall with said forward end thereof projecting into the boiler chamber.

3. In a safety device for a boiler having an outer wall and a crown sheet, a plug adapted to be threaded into the crown sheet and be removable from the furnace side thereof, the plug having an open bore in the forward end thereof of restricted diameter intermediate its ends, a rod having an anchoring element on one end extending into the bore to a point adjacent to said restricted diameter and the rod projecting therefrom outwardly of the boiler end of the plug, and soft metal anchoring said element in the bore and having a relatively thin annular wall thereof at said restricted diameter, the rod being adapted to project outwardly through the boiler wall, and cooperate with controlling means outside the boiler.

4. In a safety device for a boiler having an outer wall and a crown sheet, a plug adapted to be threaded into the crown sheet and be removable from the furnace side thereof, the plug having an open bore in its forward end, an anchor secured in the bore by soft metal, an operating rod adapted to be placed in longitudinal alignment with the anchor within the boiler and project outwardly of the boiler through said outer wall, and means providing a disengageable threaded connection between the inner end of the rod and the anchor whereby permitting said removal of the plug and the replacement thereof independently of the rod, the outer end of the rod being adapted to cooperate with controlling means outside the boiler.

FRANK L. CORMIER. HAROLD L. LARSON. 

